Optical data receiver systems

ABSTRACT

An optical data receiver for the distribution and demodulation of compressed TDM data packages comprises, optical distributor means to which the data packages are applied for selective distribution to a plurality of AWG optical demultiplexer/detector arrays, so that each demultiplexer/detector array provides in respect of each data package fed thereto from the optical distributor, a data word the bits of which are presented in parallel.

BACKGROUND OF THE INVENTION

This invention relates to optical data receiver systems and moreparticularly it relates to TDM (time division multiplexed) optical datareceiver systems. The term optical data receiver systems when usedherein, includes systems in which data is transmitted using light in thevisible and/or non-visible spectra.

Optical data receiver systems for the reception of TDM data are used intelecommunication signal routers and other high-speed fibre opticnetworks. One such system is described in the specification accompanyingour PCT Patent Publication No. WO 01/10165 A1, to which attention ishereby directed, wherein optically compressed data packets are requiredto be appropriately routed and decompressed. In such systems there is anever present requirement to increase data handling rates and to reducefabrication costs as well as size and power consumption.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an improved data receiversystem which serves to facilitate the provision of these desirablecharacteristics and which lends itself to use in telecommunication datarouters and high speed fibre optic networks and the like.

According to the present invention an optical data receiver for thedistribution and demodulation of compressed TDM data packages comprises,optical distributor means to which the data packages are applied forselective distribution to a plurality of optical demultiplexer/detectorarrays, so that each demultiplexer/detector array provides in respect ofeach data package fed thereto from the optical distributor, a data wordthe bits of which are presented in parallel.

The demultiplexer/detector array may comprise an arrayed waveguidegrating (AWG).

The optical distributor means may comprise a plurality of opticalrouting switches, one for each demultiplexer/detector array, which areoperatively associated with the demultiplexer/detector array so that TDMdata packages are selectively routed thereto as appropriate.

The routing switches may comprise optical modulators.

The modulators may each embody a semiconductor optical amplifier (SOA).

The optical amplifiers may comprise erbium doped optical amplifiers(EDOA).

The optical data receiver may form a part of a telecommunication signalrouter and be fed with TDM optical data from an optical backplane.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a generally schematic block diagram of an optical datareceiver system; and,

FIG. 2 is a schematic block diagram of a part of the system as shown inFIG. 1, wherein corresponding parts bear the same numericaldesignations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the FIG. 1 of the drawings, TDM optical signals carriedon an optical backplane 1, which may form a part of a telecommunicationssignal router for example, are fed via an optical signal distributor 2,to a demodulator unit 3 which comprises a plurality of similar demuxunits A to N, only three of which are shown for simplicity, and one ofwhich will now be described with reference to FIG. 2. As shown enlargedin FIG. 2, each of the demux units comprises an optical selector switch4, to which the TDM signals are fed via the signal distributor 2, fromthe backplane 1. Operation of each of the optical selector switches 4,is controlled via a control line 5, one for each switch, so that eachswitch opens at an appropriate instant to pass a selected one the TDMsignals to an AWG 6, (arrayed waveguide grating) with which it isoperatively associated, thereby to provide in parallel at an output port7, of a linear detector array 8, the bits of a data word correspondingto data which comprises a selected TDM signal. The mode of operation ofAWGs is well known and will not therefore be described in detail herein,except to say each data bit of a TDM signal packet, is represented by adifferent colour or frequency of light, the colours being separated androuted by the AWG 6, collected at the detector array 8, and routed todifferent output terminals of the output port 7.

The known system as described in WO 01/10165/A1, utilises a serialapproach to the decoding of each TDM packet. This has the disadvantagethat the data is received in serial format by a high-speed photodiode(e.g. 10 Gb/s or faster). This serial data then has to be electronicallyprocessed to produce a parallel data format which is thereafterprocessed by following electronic circuitry which operates at a slowerrate. This thus imposes a processing speed constrain. Use of a paralleloptical receiver as described herein, is not only faster but it reducesthe number of high-speed electronic components required, thus reducingpower consumption and potentially reducing fabrication costs and size.

In a receiver as described herein, each TDM packet is effectively splitinto its spectral components by an arrayed waveguide grating and thusdecoded in parallel format, each defined spectral component representingone bit of the compressed data. Each spectral component of a receivedpacket (i.e. each bit) is directed to a separate element of the detectorarray 8. The compressed optical data packet is thus demultiplexed andreceived as a parallel word which can thereafter interface directly withlower speed electronics (not shown). The linear detector array 8, may bebonded to the substrate of the AWG 6. The optical modulator or selectorswitch 4, may be selected from devices based on electro-absorption orelectro-optic effects, or implemented as a gated optical amplifierdepending on system requirements. Currently modulators can be realisedin InP, LiNbO3 or optical polymers. An optical amplifier may be includedto boost the optical signal, which may be integrated with the modulatoror selector switch 4. The AWG 6, may be made by processes based on,silicon on insulator, silica on silicon, or indium phosphide.

The detector array 8, would conventionally be made from a semiconductormaterial responsive to the infra-red part of the electromagneticspectrum notably the wavelengths used for fibre optic communications(examples are InGaAs, InP).

Other dispersive components such as prisms or diffraction gratings couldbe used to effect decoding and deserialisation of the packet. Theadvantages of the use of an arrayed waveguide grating are:

-   -   it is a compact planar component;    -   it may be mass-produced on a silicon substrate using the        existing manufacturing processes, which have been developed by        the electronics industry;    -   it has low waveguide losses and low coupling losses to the        single mode optical fibre and the detector array;    -   the filter characteristics of the channels can be carefully        adjusted to meet design requirements (e.g. channel bandwidth,        spectral profile, loss equalisation);    -   erbium doped waveguides could be included in the AWG design so        that optical gain could be used to boost the signal level and        thus increase the SNR (signal to noise ratio) of the detector        array 8.    -   As process technology progresses, the device could be integrated        on an integrated photonic chip made from InP thus realizing        smaller dimensions and manufacturing efficiency from using a        single manufacturing process technology. Such an implementation        is described in U.S. Pat. No. 5,689,122.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. A method for transmitting data, comprising the steps of: generating achirped optical carrier pulse; serially modulating the carrier pulsewith a data word; compressing the modulated pulse; transmitting thecompressed modulated pulse over a transport medium; receiving thecompressed modulated pulse; and decompressing the modulated pulse;wherein the method further comprises: wavelength demodulating themodulated pulse into a plurality of wavelength components, eachwavelength component representing one bit of the data word, the dataword being represented in parallel by the plurality of wavelengthcomponents.
 2. A method according to claim 1, wherein a plurality ofdata words are encoded into a sequential plurality of compressedmodulated pulses transmitted over the transport medium, furthercomprising the steps of: selecting one of the plurality of compressedmodulated pulses; and decompressing and wavelength demodulating theselected modulated pulse into a plurality of wavelength components, eachwavelength component representing one bit of the data word, the dataword being represented in parallel by the plurality of wavelengthcomponents.
 3. A method according to claim 2, further comprising thesteps of providing a plurality of selecting means, each with respectiveassociated decompression means and wavelength demodulating means, inparallel; arranging for the sequential plurality of compressed modulatedpulses to be applied to each of the selecting means; in each of theselecting means, selecting a respective one of the sequential pluralityof compressed modulated pulses; and decompressing and wavelengthdemodulating the respective selected compressed modulated pulses, eachinto a plurality of wavelength components, each wavelength componentrepresenting one bit of the data word, the data word being representedin parallel by the plurality of wavelength components.
 4. A methodaccording to claim 1, wherein the steps of decompressing and wavelengthdemodulating are performed by applying the respective compressedmodulated pulse to an optical demultiplexer/detector array.
 5. A methodaccording to claim 4, wherein the step of applying the respectivecompressed modulated pulse to an optical demultiplexer/detector arraycomprises applying the respective compressed modulated pulse to anarrayed waveguide grating (AWG).
 6. A method according to claim 5,wherein a detector array is provided, integrated with the AWG.
 7. Amethod according to claim 3, wherein the selecting means compriseoptical modulators.
 8. A method according to claim 7 wherein the opticalmodulators each embody a semiconductor optical amplifier (SOA).
 9. Amethod according to claim 7 wherein the optical modulators compriseerbium doped optical amplifiers (EDOA).
 10. A signal router arranged tooperate according to a method as defined in claim
 1. 11. An optical datareceiver for the distribution and demodulation of compressed TDM datapackages, said optical data receiver comprising optical distributormeans to which the data packages are applied for selective distributionto a plurality of optical demultiplexer/detector arrays, wherein eachdemultiplexer/detector array provides in respect of each data packagefed thereto from the optical distributor, a data word the bits of whichare presented in parallel.
 12. An optical data receiver as claimed inclaim 11, wherein the demultiplexer/detector array comprises an arrayedwaveguide grating (AWG).
 13. An optical data receiver as claimed inclaim 12, wherein the AWG is integrated with the detector array.
 14. Anoptical data receiver as claimed in claim 13, wherein the opticaldistributor means comprises a plurality of optical routing switches, onefor each demultiplexer/detector array, which are operatively associatedwith the demultiplexer/detector arrays so that TDM data packages areselectively routed thereto as appropriate.
 15. An optical data receiveras claimed in claim 14, wherein the routing switches comprise opticalmodulators.
 16. An optical data receiver as claimed in claim 15, whereinthe optical modulators each embody a semiconductor optical amplifier(SOA).
 17. An optical data receiver as claimed in claim 16, wherein theoptical amplifiers comprise erbium doped optical amplifiers (EDOA). 18.An optical data receiver as claimed in claim 11, wherein, the opticaldata receiver forms a part of a telecommunication signal router and isfed with TDM optical data from an optical backplane.
 19. A signal routerincluding a data receiver as claimed in claim 11.